Question 173894
{{{(4x+3)(3x+1)}}}


Use FOIL:


First:  {{{(highlight(4x)+3)(highlight(3x)+1)}}} : {{{4x*3x=red(12x^2)}}}


Outside:  {{{(highlight(4x)+3)(3x+highlight(1))}}} : {{{4x*1=green(4x)}}}


Inside: {{{(4x +highlight(3))(highlight(3x)+1)}}} : {{{3*3x=green(9x)}}}


Last:  {{{(4x +highlight(3)) (3x+highlight(1))}}} : {{{3*1=blue(3)}}}


Add the first degree terms {{{green(4x+9x)=green(13x)}}}


So:  {{{(4x+3)(3x+1)=red(12x^2)+green(13x)+blue(3)}}} and vice versa, of course.


The other problem works the same way.  4 times -9 is -36 plus -1 times 4 is -4 and -36 plus -4 is -40.